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Morgan.liberatore
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In which geological era did prokaryotes first appear?
Precambrian
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How can we define diversity in life or biodiversity?
- Degree of differences in:
- genetic variation
- species composition
- interactions within and between ecosystems
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What is species diversity?
commonly reserved for indices that measure both the number of species in a habitat as well as their relative abundances
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How many species have already been named?
about 1.5 million
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How many new species are named each year?
- about 13,000
- but about 3,000 are synonyms (duplicated species)
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What is tree fogging?
- technique designed by Terry Erwin in 1983
- fog one tree, killed all the species in it, then classify them all
- found 160 beetle species unique to that tree species, about 50,000 tropical tree species, beetles are about 2/5 of all insects which are about 1/2 of all species
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What is the current estimate for extant eukaryotic species?
- 3-100 million
- sir robert may's guess is 7 million
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what percentage of all species are extinct?
~99%
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what is the current estimate for how many bacteria and archaea there are?
about 10,000 bacteria species have been identified but could easily be millions or 100s of millions
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What are the 2 main factors that control diversity?
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How does area affect diversity?
In general doubling area increases number of species by 10-25%
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How does climate affect diversity?
- warm, wet areas have more species
- but we don't know why exactly
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Mammals represent ___% of diversity of eukaryotic organisms
<1%
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Beetles represent ___% of diversity of eukaryotic organisms
~22%
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What is genetic diversity?
measure of genetic distance (evolutionary separation)
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What is functional diversity?
Differences in shape, size, and generally ways of making a living (types of food, places lived, etc)
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Which group shows the greatest genetic diversity?
prokaryotes
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Which group shows the greatest functional diversity?
prokaryotes
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Where is diversity greatest geographically?
near the equator on large landmasses with good climates
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Which group of organisms are the Earth's oldest organisms?
Prokaryotes (2 major groups, bacteria and archaea)
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Which domains have a membrane enclosed nucleus?
eukarya
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Which domains have membrane enclosed organelles?
eukarya
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Which domains have peptidoglycan in the cell wall?
bacteria
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What are the defining characteristics of Archaea?
- absence of peptidoglycan in cell wall
- distinctive lipids present in their cell membranes (not found in eukaryotes or bacteria)
- many archaea also have lipid monolayer
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How does the DNA of archaea and bacteria differ from ours?
- Have single circular chromosome and plasmids
- Located in the nucleoid region
- chromosome not highly coiled
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What are plasmids?
Extra-chromosomal DNA; small rings; easily exchanged during sex
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Bactera do not have ________ organelles
membrane-bound
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What is the use of the cell membrane in bacteria?
highly folded, site of ATP synthesis & photosynthesis
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How do bacterial ribosomes differ from eukaryotes ones?
Lack of nucleus, allow simultaneous transcription and translation = fast growth and reproduction
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What are the 3 morphological differences in bacteria?
- spheres = cocci
- rods = bacilli
- helical = spirili
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How can we determine varieties in cell wall structure in bacteria?
gram staining
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What does it mean if a bacterium is gram positive?
Thick layer of peptidoglycan in the cell wall structure
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What does it mean if a bacterium is gram negative?
Thin layer of peptidoglycan in the cell wall structure between 2 membrane layers
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typically antibiotics are ineffective against gram _____ bacteria
negative
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How do bacteria reproduce?
- rapid, short generation times
- asexual reproduction - "binary fission" - literally divide in half
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How do bacteria exchange genetic material?
- 3 main methods to obtain new genetic material
- genes on plasmids are easily transferred
- in conjugation, replicated genes are transferred through hollow tubes called sex pili
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How do bacteria maintain homeostasis?
- respond to harsh environmental conditions
- move toward or away from chemicals
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what is an endospore?
- something a bacterium forms for protection
- protect bacteria from adverse conditions, helps keep it alive in harsh conditions and for a long time
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What is a biofilm?
- bacteria form surface-coating communities called biofilms
- form polysaccharide gel trapping debris and other cells
- can be hundreds of cells thick
- composed of single or many species
- an example is plaque
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What is chemotaxis?
The ability of bacteria to move towards or away from chemical signals
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How do bacteria perform chemotaxis?
- Use flagella (different than eukaryotes - made from different protein, thinner, more numerous)
- Also glide, roll, use gas floats inside cell
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How do bacteria transform energy?
- despite their simplicity in cell structure, prokaryotes are extremely diverse in their metabolic abilities
- variety due to diverse habitats and long evolutionary history
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What are photoautotrophic bacteria like?
- Transform light energy into chemical energy = photosynthesis
- absorb light energy with chlorophyll
- use light energy to convert CO2 into glucose
- produce O2 as a waste product
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What are aerobes?
obligate aerobes must use oxygen for long-term metabolism
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what are anaerobes?
- do not require oxygen for metabolism
- make ATP using fermentation, not cellular respiration
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What are obligate anaerobes?
oxygen is toxic to them
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What are facultative anaerobes?
use oxygen if it's available
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What are aerotolerant anaerobes?
can survive in oxygen environment but do not use oxygen
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Most prokaryotes and other organisms do what to get energy?
- they are chemoheterotrophs
- consume organic molecules for carbon and energy source
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What are some of the roles that heterotrophic prokaryotes can play in the biosphere?
- decomposers
- symbiosis with eukaryotes (like herbivores)
- pathogens
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What do nitrogen fixing bacteria do?
Why is this important?
- convert atmospheric N to NH3
- plants are dependent on nitrogen-fixation
- crop rotation often involves planting legumes (N-fixing bacteria often live on roots of legumes)
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How is illness to host caused by pathogenic bacteria?
Caused by toxins
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What are exotoxins?
- secreted proteins, very toxic
- example: botulism, tetanus
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What are endotoxins?
- outer bacterial membrane, rarely fatal
- example: salmonella and E. coli (food poisoning)
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How are bacteria classified?
- Traditionally by shape and gram stain
- Now based more on DNA sequencing
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